Flutter Notes｜Flutter-Apk 大小优化探索

追逐，探索，永不停歇～

前言

还记得刚入坑 Flutter 打包时，被深深震惊了一番，卧槽，这包好大！

• ✓ Built build/app/outputs/apk/release/app-release.apk (23.8MB).

足足将近 24 MB，第一反应真的懵逼了。

固然直接提交市场后，也是被人各类 diss，缘由仍是没什么功能，包贼大，用户下载贼不舒服。

强烈要求优化 Apk 大小。

既然是探索，前提我仍是个刚入 Flutter 坑的小白白，因此嘛，不免不全面，欢迎各位大佬拍砖、指点～

探索之路 一部曲

首先，我首次打包的方式以下：

雷同使用下面的命令（默认带有 --release）：

• flutter build apk

1、熊猫压缩法（减小 0.7 MB）

首先第一想法，图片我没作压缩，一样通过查看后，发现图片在 apk 占比为 4.1% ：

• 2.3 % Flutter 引用到的资源文件；
• 1.8% Android 启动页的背景图。

最后，咱们经过国宝之手试试最后能减小多少？

这里分别针对 Flutter 下图片资源、Android/iOS 启动页进行压缩。

再次运行 build apk 后，完成输出以下日志：

• ✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB).

再来看 Apk 中图片的占比以及下降到 1%：

最终 Apk 大小直接减小了 0.7 MB，仍是比较爽的。

2、so 优化大法（减小 14 MB）

作 Android 的小伙伴知道，对于咱们这些小厂没能力搞动态下发 so 的小渣渣而言，只能默默逆向大厂 Apk，看看人家是怎么作的，而后借（抄）鉴（袭）。

针对 Flutter 打出的 Apk 包，排在第一位的即是 lib，占比 86.4%，足足有 19.6 MB：

这里看到将咱们编写的 Dart 代码转化为不一样架构下的 so 库，以供原生调用（我是这么猜想的哈）。

针对不一样 CPU 架构所表明含义，尤为 Flutter 打包 Apk 生成的三种 CPU 架构分别对应什么含义：

• x86_64： Intel 64 位，通常用于平板或者模拟器，支持 x86 以及 x86_64 CPU 架构设备。
• arm64-v8a： 第 8 代 64 位，包含 AArch3二、AArch64 两个执行状态，且对应 32 、64 bit，而且支持 armeabi、armeabi-v7a 以及 arm64-v8a。
• armeabi-v7a： 第 7 代 arm v7，使用硬件浮点运算，具备高级拓展功能，兼容 armeabi 以及 armeabi-v7a，并且目前大部分手机都是这个架构。

其实咱们第一次经过 flutter build apk 命令生成 apk 时，Google 这里已经为咱们提示了：

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app master ● flutter build apk
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size. To generate an app bundle, run: flutter build appbundle --target-platform android-arm,android-arm64,android-x64 Learn more on: https://developer.android.com/guide/app-bundle To split the APKs per ABI, run: flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split Running Gradle task 'assembleRelease'... Running Gradle task 'assembleRelease'... Done 13.8s ✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB). 复制代码

接下来经过如下命令进行分别打包（构建指定 CPU 架构类型 Apk 包）：

• flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi

这里解释下这个命令的含义：

• 首先 flutter build apk 表示当前构建 release 包；
• 后面 android-arm,android-arm64,android-x64 则是指定生成对应架构的 release 包；
• 最后的 --split-per-abi 则表示告知须要按照咱们指定的类型分别打包，若是移除则直接构建包含全部 CPU 架构的 Apk 包。

因此这个命令的含义就是告诉编译器，我须要你为我针对我指定的三种不一样架构分别生成对应的 Apk 包。

有的小伙伴就说了，你这空口无凭，没证据啊。

好，我给你运行一波～

• 验证：flutter build apk --target-platform android-arm,android-arm64,android-x64 结果

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●  flutter build apk --target-platform android-arm,android-arm64,android-x64                
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size. To generate an app bundle, run: flutter build appbundle --target-platform android-arm,android-arm64,android-x64 Learn more on: https://developer.android.com/guide/app-bundle To split the APKs per ABI, run: flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split Removed unused resources: Binary resource data reduced from 817KB to 815KB: Removed 0% Running Gradle task 'assembleRelease'... Running Gradle task 'assembleRelease'... Done 115.8s ✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB). 复制代码

看见没，事实论证结果。

最后，咱们采起告知编译器为咱们生成指定 CPU 架构的 Apk 的方式，并查看对应输出日志信息：

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●  flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi                                         
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Running Gradle task 'assembleRelease'...                                
Running Gradle task 'assembleRelease'... Done                      36.0s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.8MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (10.1MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (10.2MB).
复制代码

看看 app-armeabi-v7a-release.apk 包大小，结果是否是贼喜人？由 23.8 MB 直接减小到 9.8 MB。

随后咱们看下对应的 apk 内容：

lib 占比也从原来的 86.4%，19.6 MB 直接减小为 67.2%，大小 6.3 MB。

3、混淆大法好（减小 0.4 MB）

还记得 Android 混淆的魅力吗？

• 增长逆向难度；
• 减小 Apk 大小；
• 。。。

对此 Flutter 也为咱们提供了混淆命令：

• flutter build apk --obfuscate --split-debug-info=//

简单说下我我的对于此命令的理解：

• --obfuscate：开启混淆操做；
• --split-debug-info=：将因混淆生成的 map 符号表缓存到此位置。

这里咱们先测试下，直接构建完整包，并添加混淆操做，输出的 apk 大小有多少：

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●  flutter build apk --obfuscate --split-debug-info=HLQ_Struggle
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size. To generate an app bundle, run: flutter build appbundle --target-platform android-arm,android-arm64,android-x64 Learn more on: https://developer.android.com/guide/app-bundle To split the APKs per ABI, run: flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split Running Gradle task 'assembleRelease'... Running Gradle task 'assembleRelease'... Done 60.3s ✓ Built build/app/outputs/apk/release/app-release.apk (21.9MB). 复制代码

一样也在项目根目录下生成了符号文件：

相比一开始的 23.8 MB，减小了 1.9 MB。那么咱们直接针对不一样 CPU 生成对应的 Apk 并添加混淆结果又是怎样呢？

➜  xxx_app git:(master) ✗ flutter build apk --obfuscate --split-debug-info=debugInfo  --target-platform android-arm,android-arm64,android-x64 --split-per-abi                                       
Running Gradle task 'assembleRelease'...                                
Running Gradle task 'assembleRelease'... Done                      39.3s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
复制代码

未混淆的 v7a 大小与开启混淆相比，开启混淆减小了 0.4 MB。

还不错。

对于混淆的文件，出问题怎么调试呢？

莫慌，Flutter 一样提供了 symbolize 神器，固然这个不在涉猎范围内，就不详细解释了，知道就好：

heliquan@Mac  ~/CodePro/FlutterPro/haozhuan_app   master ●  flutter symbolize -h
Symbolize a stack trace from an AOT compiled flutter application.

Usage: flutter symbolize [arguments]
-h, --help                                                                     Print this usage information.
-d, --debug-info=</out/android/app.arm64.symbols>                              A path to the symbols file generated with "--split-debug-info".
-i, --input=</crashes/stack_trace.err>                                         A file path containing a Dart stack trace.
-o, --output=<A file path for a symbolicated stack trace to be written to.>    

Run "flutter help" to see global options.
复制代码

End

上面叨叨半天，总结一个比较有用的命令：

• flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi

含义就是，哥，帮我针对不一样 CPU 架构分别打包，别忘记混淆哈，生成的符号表文件记得帮我放在 HLQ_Struggle 目录下。

详细日志以下：

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●   flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi                                          
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Running Gradle task 'assembleRelease'...                                
Running Gradle task 'assembleRelease'... Done                      36.9s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
复制代码

固然也有小伙伴说了，打包前 clean 下，生成的包会小，实际测试一下：

heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●  flutter clean           
Cleaning Xcode workspace...                                         3.3s
Deleting build...                                                2,774ms (!)
Deleting .dart_tool...                                              41ms
Deleting Generated.xcconfig...                                       0ms
Deleting flutter_export_environment.sh...                            0ms
Deleting App.framework...                                            9ms
 heliquan@Mac  ~/CodePro/FlutterPro/xxx_app   master ●   flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi                                          
Running Gradle task 'assembleRelease'...                                                                                                                                                  Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%                             
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%                             
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%                             
Running Gradle task 'assembleRelease'...                                                                           
Running Gradle task 'assembleRelease'... Done                     215.3s (!)
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
复制代码

根据以上输出结果，并没发现减小了哪儿。

一点小经历分享，固然确定会有更好的操做方法，可是目前仅次于此，欢迎各位大佬交流～

Thanks

• 熊猫压缩法
• Flutter apk最简单的瘦身方式
• Android ABI
• Build an APK
• 混淆Dart代码
• 测量你的应用体积
• Flutter apps are too big in size
• Build and release an Android app
• How to decrease the size of app.framework on iOS? #21813：看得我各类懵